Dual functionality of twin-arginine signal peptides

原核生物是人类已知的最简单、最真实的生物。它们包括单细胞细菌和它们的近亲古生菌，它们可能是现存的最早的细胞生命形式中最接近的幸存例子。这些生物中的许多可以在没有氧气的情况下生存和生长，而是利用环境中的其他化学物质来产生生命所需的能量，而硝酸盐等富含氮的化学物质在原核生物的整个光谱中都被非常普遍地用作替代品。为了从硝酸盐中获取能量，原核生物含有特殊的蛋白质或酶，其中许多蛋白质或酶由许多不同的部分或亚单位组成，它们本身通常含有金属和硫原子。此外，这些酶经常在细胞表面的‘外面’被发现。这些酶是如何走出细胞的，以及它们是如何与之前连接的所有金属和亚基完全组装在一起的，这是这项研究项目的重点。大多数注定位于细胞外的酶都可以通过它们身上存在的特殊‘信号’来识别。我们发现，这种同样由蛋白质组成的信号在细胞中有两种功能。首先，它有助于组装亚基和金属，其次，它有助于将完成的酶定位在细胞外。我们想要孤立地研究这些函数，不受另一个函数的干扰，以便全面而详细地理解它们。然后，我们将再次查看完整的系统，并应用我们的新知识来理解这两个功能是如何协调工作的。一旦我们详细了解了这些过程是如何工作的，我们就可以让它工作得更好，这样生物技术公司就可以用它来制造有用的日常产品。或者，我们或许能够学习如何设计一种新的抗生素，在不损害环境的情况下停止这个系统的工作--一些无法执行这些任务的致命细菌不再危险。

Prokaryotes are the simplest truly living organisms known to man. They include the single-celled bacteria and their cousins the archaea, probably the closest surviving examples of the earliest cellular life-forms that ever existed. Many of these organisms can live and grow without oxygen, and instead utilise other chemicals from the environment to generate energy for life and nitrogen-rich chemicals such as nitrates are very commonly used as a replacement across the whole spectrum of prokaryotes. To get energy from nitrate prokaryotes contain special proteins or enzymes, many of which are made-up of lots of different parts, or subunits, which in themselves often contain metal and sulphur atoms. In addition, these enzymes are often found 'outside' on the surface of the cell. How these enzymes get out the cell, and how they are fully assembled with all their metals and subunits attached before that, is the thrust of this research project. Most enzymes that are destined to be located outside the cell are identifiable by the presence of a special 'signal' on them. We have found this signal, which is also made of protein, has two jobs in the cell. First, it helps to assemble the subunits and metals, then second, it helps to locate the finished enzyme outside the cell. We want to study these functions in isolation, without interference from the other one, in order to understand them fully and in detail. We will then look again at the complete system and applying our new knowledge to understand how the two functions work together in harmony. Once we learn in detail how these processes work we may be able to make it work 'better' so that biotechnology companies can use it to make useful everyday products. Or we may be able to learn how design a new antibiotic to stop this system working without harming the environment - some deadly bacteria that cannot perform these tasks are no longer dangerous.